When a child table doesn't have its FK indexed, whether the lock will affect only the parent row or the whole parent table?

Suppose I have the following tables

PARENT ( colp number not null primary key,
col2 number );

CHILD ( COLc number not null Primary Key,
COLp number,
COLx number,
constraint fk_colp foreign key (colp) references PARENT(colp)
) ;

Assume that I do not have index defined on "colp" of CHILD.

Now when I delete/insert/update a record from CHILD table, what kind of Lock it acquires on the parent table?.

Will it acquire any lock, if the parent row is not at all afected?
(say insert or update on colx)

If it acquires any lock for any of the DML, will it just Lock the Parent record or it acquires a lock on the entire table?

What is the case when the operation is on the PARENT table?

Note: I went thru many of the documents (metalink) and couldn't decide whether the lock is just on the parent records or on the entire table?